MIC offload.h

最新推荐文章于 2021-01-26 14:34:42 发布

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最新推荐文章于 2021-01-26 14:34:42 发布

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本文介绍了如何使用Intel的_offload.h头文件进行MIC（Intel Xeon Phi协处理器）设备管理和并行处理。通过示例代码展示了获取MIC设备数量、设备编号、处理器数目以及最大支持线程数的方法，并探讨了环境变量如何影响并行线程数。

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Intel编译器include文件夹下有MIC的头文件：offload.h

列举几个常用的函数说明：

_Offload_number_of_devices() //获取MIC数目

_Offload_get_device_number() //获取MIC编号

omp_get_max_threads_target(TARGET_MIC, 0) //获取MIC上可以最多支持的线程数

omp_get_num_procs_target(TARGET_MIC, 0) //获取MIC上的处理器数目

测试代码：

#include <stdio.h>
#include "offload.h"

int main(int argc, char **argv)
{
printf("_Offload_number_of_devices()=%d\n",_Offload_number_of_devices());
printf("host: _Offload_get_device_number()=%d\n",_Offload_get_device_number());
printf("host: _Offload_get_physical_device_number()=%d\n\n",_Offload_get_physical_device_number());
if(_Offload_number_of_devices()>=1)
{
#pragma offload target(mic:0)
{
printf("mic0: _Offload_get_device_number()=%d\n",_Offload_get_device_number());
printf("mic0: _Offload_get_physical_device_number()=%d\n\n",_Offload_get_physical_device_number());
}
}
if(_Offload_number_of_devices()>=2)
{
#pragma offload target(mic:1)
{
printf("mic1: _Offload_get_device_number()=%d\n",_Offload_get_device_number());
printf("mic1: _Offload_get_physical_device_number()=%d\n\n",_Offload_get_physical_device_number());
}
}

printf("omp_get_max_threads_target(TARGET_MIC, 0)=%d\n",omp_get_max_threads_target(TARGET_MIC, 0));
printf("omp_get_num_procs_target(TARGET_MIC, 0)=%d\n\n",omp_get_num_procs_target(TARGET_MIC, 0));

return 0;
}

运行结果：

_Offload_number_of_devices()=2
host: _Offload_get_device_number()=-1
host: _Offload_get_physical_device_number()=-1

omp_get_default_device()=0
omp_get_num_devices()=2

omp_get_max_threads_target(TARGET_MIC, 0)=240 //7110P上运行的结果，7110P有61个核，1个运行uos，其它每个核上可以运行4个线程，所以这里显示的是240
omp_get_num_procs_target(TARGET_MIC, 0)=240

mic1: _Offload_get_device_number()=1
mic1: _Offload_get_physical_device_number()=1

mic0: _Offload_get_device_number()=0
mic0: _Offload_get_physical_device_number()=0

设置环境变量：

export MIC_ENV_PREFIX=MIC

export MIC_OMP_NUM_THREADS=180

再次运行结果：

_Offload_number_of_devices()=2
host: _Offload_get_device_number()=-1
host: _Offload_get_physical_device_number()=-1

omp_get_default_device()=0
omp_get_num_devices()=2

omp_get_max_threads_target(TARGET_MIC, 0)=180 //环境变量MIC_OMP_NUM_THREADS改变omp_get_max_threads_target的值
omp_get_num_procs_target(TARGET_MIC, 0)=240

mic1: _Offload_get_device_number()=1
mic1: _Offload_get_physical_device_number()=1

mic0: _Offload_get_device_number()=0
mic0: _Offload_get_physical_device_number()=0